The largest planet in our solar system is by far Jupiter, which beats out all the other planets in both mass and volume. Its name refers to the god of the sky and thunder and king of the gods in Ancient Roman religion and mythology.
Jupiter’s diameter, at 140 000 km, is about 11 times Earth’s diameter. Despite its bulk, though, Jupiter has a fast rotation period of only 10 hours.
Jupiter is mostly swirling gases and liquids. Like the sun, the planet is predominantly composed of hydrogen and helium. But unlike the sun, it lacks the necessary amount to begin fusion, the process that fuels a star. This is why this gas giant is a giant planet also called “failed star”, like Saturn. Deep in the atmosphere, pressure and temperature increase, compressing the hydrogen gas into a liquid. This gives Jupiter the largest ocean in the solar system : an ocean made of hydrogen instead of water. Scientists think that, at depths perhaps halfway to the planet’s center, the pressure becomes so great that electrons are squeezed off the hydrogen atoms, making the liquid electrically conducting like metal.
Jupiter forms a kind of miniature solar system. In 1610, the Italian scientist Galileo Galilei observed through its telescope the four largest moons of Jupiter : Io, Europe, Ganymède and Callisto. Jupiter atmosphere produces the well-known Great Red Spot, the largest anticyclonic storm in the Solar System, continuously observed since 1878.
Nine spacecraft have studied Jupiter up close. NASA’s Juno spacecraft is currently studying the gas giant planet. A multitude of magnificent, swirling clouds is captured from orbit. The bright clouds are most likely ammonia or ammonia and water, mixed with a sprinkling of unknown chemical ingredients.